Proton Radiation Therapy

Proton Beam Principles

Protons have a physical advantage over gamma rays, photon rays and x-rays when it comes to sparing normal tissues. Protons lose only a small amount of energy when they enter the body. Their remaining energy is released when they reach the tumor, delivering the most effective dose of radiation. Proton beams have no exit dose unlike conventional radiation therapy and how deeply the radiation penetrates is calculated based on the tumor's location. Irregularly shaped lesions with awkward configurations near critical structures are well suited for proton beam therapy.


Protons deposit most of their radiation energy in what is known as the Bragg peak, which occurs at the point of greatest penetration of the protons in tissue. The exact depth to which protons penetrate, and at which the Bragg peak occurs, is dependent on the energy of the proton beam. This energy can be very precisely controlled to place the Bragg peak within a tumor or other tissues that are targeted to receive the radiation dose. Because the protons are absorbed at this point, normal tissues beyond the target receive very little or no radiation.


There are currently 14 Proton Centers now in operation and 12 new centers in development in the US. The three sites that have been most reported as being their choice for ACCOI members have been:

Midwest Proton Institute, Bloomington, IN

Loma Linda Medical Center, Loma Linda, CA

Massachusetts General Hospital, Boston, MA

Here is the link of the National Association for Proton Therapy